An air purification device which is equipped with a discharge device has been used as a means for decomposing and removing, by a plasma generated by electric discharge, components (such as odorous components, harmful components, and other contaminants) to be treated that are contained in a stream of air to be treated. One such purification device is an air purification device of the streamer discharge type in which a low temperature plasma is produced by streamer discharge and which is regarded as a preferable technology for decomposing and deodorizing harmful components because it can provide higher air purification efficiency in comparison with air purification devices of other discharge types (for example, glow discharge type air purification devices and corona discharge type air purification devices).
With reference to FIG. 13, there is shown a typical streamer discharge type air purification device which includes, as a discharge device (80), discharge electrodes (81) and counter electrodes (82) facing the discharge electrodes (81). The discharge electrodes (81) are arranged in parallel at predetermined intervals on a substrate (83). Each discharge electrode (81) is formed such that it has a projecting tip. On the other hand, the counter electrodes (82) are arranged at predetermined intervals on both sides of the substrate of the discharge electrodes (81). And the tips of the discharge electrodes (81) and the counter electrodes (82) are positioned face to face with each other. In addition, the air purification device further includes an electric power supply means (not shown) configured to apply voltages to both the electrodes (81, 82) and an air blower means (not shown) by which a stream of air to be treated is distributed to the discharge device (80). In this configuration, when the air blower means is activated and the electric power supply means applies voltages to both the electrodes (81, 82), a streamer discharge is generated between both the electrodes (81, 82), thereby generating a low temperature plasma. Components contained in a stream of air to be treated are brought into aeration contact with activated species (fast electron, ion, radical, other excited molecule et cetera) produced as a result of generation of the low temperature plasma, whereby these components to be treated are decomposed and removed from the air stream (see Patent Document I).    Patent Document I: JP 2001-218828A